There was much agonising before the bombing was carried out - the Archbishop of Canterbury was against it - and much debate afterwards whether it had been the right thing to do, from a tactical or moral perspective.

Most experts believe there were no Germans inside the monastery before the bombing.

But years later, as the chairman of the Monte Cassino Veterans' Association, Mr Clarke met one of the few monks who was in the monastery at the time of the bombing, Agustino Sacameno, who told him a different story.

The monk took him into the chambers below the restored monastery, near the 1,400-year-old tomb of Saint Benedict, and said 300 people had sheltered there as the bombs fell, including some Germans.

A young British artillery officer, Peter Holloway, arrived at Monte Cassino a month after the bombing and soon found himself within a few hundred yards of the ruined monastery.

He spent four days in a "sangar" - a hollow scraped out of the stony ground, with stones piled up around it - directing the fire of his battery.

Golden rain

"The Company put on a night attack and I gave what observations I could," he has written in a contribution to the BBCi History People's War site.

"The artillery support was pretty to watch, falling all around the monastery and surrounding slopes, making patterns of golden rain and dull red bursts of flame.

You had only to see the monastery to know that a direct attack was madness

Peter Holloway

"A machine gun opened up with tracer but soon stopped as the shell bursts came closer. When daylight came, not a sign of movement anywhere."

Like Mr Clarke, he regards the destruction of the monastery as a "pointless exercise", and describes the whole strategy of the battle of Monte Cassino as a "disaster".

"You had only to see it to know that a direct attack was madness," Mr Holloway says, adding that the 4th Indian Division, to which his regiment was attached, showed elsewhere in Italy the wisdom of going round a target rather than tackling it head on.

Mr Clarke, who took part in three of the four main battles at Monte Cassino, says bad organisation partly accounts for the huge death toll.

But he also says that the German troops involved were some of the best in the German army - including paratroopers and Panzer grenadiers - who were bound to put up a strong fight.

The fact that they were tied down in Italy also meant they were not on hand for D-Day when it occurred, shortly afterwards.

"We 'liberated Europe' nine months before D-Day," he says. "Naples in October, Cassino in May, then Rome. People forget that."